This code should be in `client/karma.js` rather than inlined here. Feel free to keep the `<iframe>` here in the template. And the client Karma object will decide based on the config (passed to `execute`) - if `useIframe` is false, then it will do `window.open()`, otherwise use the iframe. If there is no window, create one (so that even if I close the popup window and then Karma tries to run, it will re-create the window).